An anonymous reader quotes a report from The Independent: Astronauts who venture into deep space appear to be much more likely to die from heart disease, according to a new study. In another sign that leaving planet Earth is fraught with danger and a potential blow to hopes of establishing a colony on Mars, researchers discovered deep space radiation appears to damage the body's cardiovascular system. They reported that three out of the seven dead Apollo astronauts died as a result of a cardiovascular disease, such as a heart attack or stroke. Although the numbers are small, that rate of 43 percent is four to five times higher than found among astronauts who flew in low Earth orbit or who did not actually go into space, according to a paper in the journal Scientific Reports. In an attempt to test whether the higher numbers of cardiovascular deaths were simply a statistical blip or a genuine sign of the effect of traveling into deep space, the scientists exposed mice to the same type of radiation that the astronauts would have experienced. After six months, which is the equivalent of 20 human years, the mice showed damage to arteries that is known to lead to the development of cardiovascular disease in humans.